In industrial and manufacturing processes, many products require heating at high temperatures, such as 300.degree. F. up to 1000.degree. F., in order to drive off water vapor. Products such as plywood, veneer board, ceiling tile, and gypsum board require drying in large volumes, which is often accomplished in continuously fed, roller-type drying ovens. Typically, the oven temperature is held constant, while the boards are continuously fed through the oven on powered rollers.
Such powered rollers conventionally are held in position by bearing assemblies mounted on an oven frame. Because the oven temperatures are too high for oil or grease lubricated bearings, self-lubricating carbon/graphite bearings are normally used. Because such bearings require periodic replacement, the carbon/graphite material is usually press-fit into a steel sleeve and forms a replaceable cartridge, for example, as shown in U.S. Pat. No. 3,160,449 assigned to Metallized Carbon Corp.
On the driven end of the rollers, a conventional replaceable cartridge has a shroud carrying a bushing split into two halves which can be taken apart during replacement, thus avoiding the need to remove the roller drive chain and sprocket, for example, as shown in U.S. Pat. No. 3,022,126. Another type has a split bearing structure with concentric split bushing halves, as disclosed in U.S. Pat. No. 3,383,142, also assigned to Metallized Carbon Corp. However, because the shroud and carbon/graphite bushing are split, it is not possible to press-fit the bushing into the shroud. As a result, the carbon/graphite bushing is not held securely and may move with the journal. Turning with the journal causes the outside circumference of the carbon/graphite bushing to wear and eventually to fall out of the shroud.